The present invention relates to a papermaking headbox in general, and tools to assist with the assembly and disassembly of the headbox in particular.
In a papermaking machine, fibers such as wood fibers are suspended in a dilute suspension in water and supplied onto a single forming fabric, or between two forming fabrics such that a paper web is formed. The web formed is first dewatered in a forming section and further dewatered through pressing in a pressing section, followed by final dewatering in a dryer section by application of the heat generated by steam heated dryer rolls. Critical to the overall quality of the web of paper or board formed in the papermaking machine is the condition of the fibers as they are supplied to the forming section. Ideally the fibers are evenly distributed in a cross machine direction extending across the width of the web, and are deposited before the fibers have a chance to clump together. To accomplish these goals sophisticated devices known as headboxes supply to the fabric or fabrics an even jet of stock composed of water, fibers and various additives.
Carefully formulated fiber stock is supplied to a header in the headbox which evenly distributes the stock in the cross machine direction to a flow channel which leads to a slice chamber and then to a slice opening which discharges on to the forming fabric(s) in the forming section. As the stock proceeds from the inlet header it typically passes through a turbulence generator and then into a converging slice chamber to the narrow slice opening formed by slice lips. A jet of stock closely matching the velocity of the forming fabric(s) exits the headbox through the slice lips and flows onto the forming fabric(s). The upper portion of the slice chamber is formed by a beam hingedly mounted by a knuckle to the headbox. Periodically during machine maintenance it is necessary to remove the slice beam from the headbox for cleaning and inspection.
Because of the high cost of ownership of the papermaking machine, such machines are typically operated as nearly continuously as possible. Scheduled maintenance throughout the machine is simultaneously performed at certain intervals to avoid unscheduled shutdowns. During scheduled maintenance the availability of overhead crane(s) for moving heavy objects is limited by the competing needs of the various sections of the papermaking machine which also require use of an overhead crane. Typically the slice beam, which can weigh in the neighborhood of 20,000 pounds, requires the availability of a crane for its removal and reinstallation to the headbox. Furthermore, the slice beam normally contains a large number of electrical or hydraulic actuators which shape the slice lip to control small-scale variations in the paper web produced. Complete removal of the slice beam requires disconnecting and reconnecting numerous control and power lines. What is needed is a system for removing and reinstalling the headbox slice beam with minimum use of the overhead crane, and which avoids the necessity of disconnecting the slice lip control connections.